Automatic draft regulator



Oct. 10, 1933. SPEAR 1,929,758

AUTOMATIC DRAFT REGULATOR Filed April 6, 1932 INVENTOR. LEOLYN FSPEA R ATTORNEYS.

an axis of rotation for the damper which is the face of the damper.

, tical plane as that of the dampers, axis and wing, in which:

Patented Oct. 10, 1933 AUTOMATIC DRAFT REGULATOR Leolyn F. Spear, Westfield, .Mass., assignor to Gilbert & Barker Manufacturing Company, ,West Springfield, Massr, a corporation of Massachusetts Application April 6, 1932. Serial No; 603,583 "3 Claims. (01. 23 -45 This invention relates to improvements in maintained substantially constant at a predeautomatic draft regulators. termined value, and A is an air inlet to this The invention has for its object the provision flue, which inlet is controlled by the damper D. of an improved pivotal mounting of the draft This damper is supported for swinging movecontrolling damper, characterized by the incliment in a novel manner from ring R, mounted nation of the axis of rotation to the face of within pipe A near the inlet end thereof, and the damper, whereby, when such axis is mounted suitably fixed thereto. Damper D can swing inin an approximately vertical position, the center wardly from the fully closed position shown in of gravity of the damper will be raised as ,it Figs. 1, 2 and 4 to the fully open position shown swings open and the weight of the damper will in Figs. 3 and 5. Stops 8 and 9, fixed to ring serve as the force to swing the damper back into R, limit the extent of swinging movement of closed position. the damper,-the stop 8 holding the damper Another object of the invention is to provide against outward swinging movement beyond its closed position and the stop 9 holding the damper from inward swinging movement beyond its open position.

One of the important features of the mounting of the damper is that its axis of rotation is inclined at an acute angle to the plane of the damper disc. As shown in Fig. 1, the pivot rod 10, which is supported in suitable upper and lower bearings 11 and 12 provided in ring Rand to which disc D is fixedby the bracket 13, slopes downwardly and rearwardly away from disc D. By this arrangement,.the center of gravity of the damper is caused to rise progressively as the damper moves from closed to open position as will be clear from a comparison of Figs. 2 and. 3. Thus, the weight of thedamper is made to serve as the force for moving the damper to closed position. In addition, the axis of the damper is preferably also inclined in the manner shown in Fig. 2. That is, its axis, when looking squarely at the rear face of the damper, is in downwardly convergent relation with respect to the vertical center line of the damper. The first feature may be used without the second feature (that is the bearings 11 and 12 might be vertically in line) but the preferred arrangement is that illustrated, in which the two features are combined. The second feature is of importance in securing a balanceof the damper when in open position. Its weight is then so located as to exert substantially no turning force on the damper. Exact balance would necessitate having the center of gravity of the damper lie in a vertical plane such as that represented at p in Fig. 5, passed through both pivot points 11 and 12. Exact balance is not desired because there must exist a slight tendency to move the damper back to closed position. Therefore, as will be seen in Fig. 5, the center of the damper lies just slightly to the right of plane p. By turning the ring R in pipe A to the right or left as viewed in Fig. 2, one can find the proper inclination of rod 10 where the damper not only inclined in the manner above set forth but is also inclined in downwardly converging relation with the vertical center line of the damper, when considered as looking squarely at By this arrangement, the damper when in fully open position may be substantially balanced,- that is its center of gravity may be then moved into such position that it lies in the same veraccordingly exerts no tendency to move the damper back into closed position. While exact balance is not desired (there must be a small force for returning the damper to closed position) it is desired to secure a resistance to opening of the damper which decreases progressively as thedamper opens and one which decreases in substantially the same proportion as does the force operating to open the damper. These and other objects will best appear as the detailed description proceeds and will be pointed out in the appended'claims.

The invention will be disclosed for illustrative purposeswith reference to the accompanying Fig. 1 is a side elevational View, partly in section, showing aflue pipe'in which the draft regulator is 'mounted,'the damper of such regulator being shown infully closed'position;

Fig. 2 is a cross sectional view taken on the line 22' of Fig. 1;

Fig. 3 is a view taken similarly to Fig. 2 but showing the damper in-fullyopen position;

Fig. 4 is a sectional plan view'taken on the line 4-4 of Fig. 2; y

Fig. 5 is a plan view looking from thetop of Fig. 3; and

Figs. 6 and 7 are cross sectional views showing two modifications. I

Referring to the drawing; F indicates a flue or other passage, in which the draft is to be is nearly balanced when in fully open position, but still has a slight tendency to return to closed position. Such inclination of the pivot rod is shown in Fig. 2.

It is a desirable condition to have the resistance to opening movement of the damper decrease progressively as the damper opens and in proportion to the progressive decrease in the force operating to open the damper. Such force is the differential in pressure between atmospheric air outside pipe A and the gases inside flue F. This pressure differential acts initially on the full area of damper D, and insofar as it acts on the segmental area to the right of rod 10 it tends to close the damper but since the remaining area is much larger, the predominating tendency is to open the damper. The opening force would be the pressure difierential multiplied by an area equal to the full area of the damper minus that of two of the segmental portions referred to. This pressure acts in a direction parallel to the axis of pipe A and, as the damper opens, its projected area taken in directions parallel to the axis of pipe A, progressively decreases. The opposing force,-the weight of the damper,acts through a moment arm which progressively decreases as the damper opens. Initially this moment arm is relatively large as shown at m in Fig. 4. This moment arm gradually becomes shorter as the damper opens and would, of course,become zero if and when the damper reached a position of exact equilibrium. Actually, it does not quite reach such position exactly for the reasons above set forth but it approaches very closely thereto. The moment arm, as shown at m in Fig. 5, is very small when the damper is fully open. Accordingly, the resistance to opening of the damper progressively decreases as it opens and, while such resistance does not necessarily decrease exactly in the same proportion as the opening force, it is substantially so and near enough for all practical purposes. The desired result of having the damper move from fully closed to fully open position without a very great change in the pressure differential is secured and that is the thing which it is desired to accomplish.

The damper may be of thin sheet metal, as for example, tin plate. It possesses little inertia and, properly mounted, is exceedingly sensitive and will maintain the draft, within narrow limits, at substantially a constant value. In addition, the draft regulator is exceedingly simple and inexpensive to make. It involves simply a circular disc of thin sheet metal, a pivot rod with some simple bracket for attaching the rod to the disc, together with the ring R which may be a cast ing, and the adjustable bearings 11 and 12 of the same general nature as set screws.

If variation of the pressure at which the damper opens is required, any suitable adjustable counterweight may be applied to damper D. For example, a weight 15 may be secured to the damper as best shown in Fig. 3 and the damper may be mounted for rotary adjustment about its center. That is, the damper may be secured to bracket '13 by a screw and nut 16 and 17, respectively. By loosening nut 1'7 slightly the damper may be turned about the axis of screw 16 to position weight 15 at various distances to the right 'or left of the vertical center line of the damper.

It is not essential that the pivot rod be straight as shown. It might be in the crank form shown at 10' in Fig. 6 and directly secured to the damper D as by soldering, brazing or welding or the like. The bearings 11' and 12 correspond with the bearings 11 and 12 above described. This arrangement is identical in principal and operation with that described because the axis of rotation, represented by the dot dash line 18 is inclined in the same manner asabove described.

In Fig. '7 a second modification is shown, characterized by the provision of means for varying the angular relation between the face of the damper and the axis of rotation thereof. The pivot rod 10 is mounted in ring R, or any other suitable form of marginally embordering frame for the damper, as before. The damper D, however, is hingedly connected near its upper end to the pivotrod by a U-shaped clip 20, one leg of which may be welded or otherwise suitably secured to the pivot rod and the other leg of which is similarly secured to the damper. Near its lower end the pivot rod carries a nut 21. A screw 22, mounted to turn in damper D but held against axial movement relatively thereto as in dicated, is threaded into nut 21. Thus, by turning screw 22, the damper may be swung toward or away from its pivot rod to vary the angle therebetween. This provision varies the extent to which the center of gravity of the damper rises and falls as the damper opens and closes and thus enables a variation of the pressure at which the damper D will open. Necessarily, the counterweight, such as 15, can be dispensed withsince the adjustment just described has the same purpose in view.

As herein shown, the damper is supported within a frame which emborders its margin and such frame is of ring form. It should be obvious that periphery. The purpose of this'arrangement is to provide clearance in pipe A to allow'for the rising movement of the damper.

The invention has been disclosed herein, in an embodiment at present preferred, for illustrative purposes, but the scope of the invention is defined by the appended claims rather than by the foregoing description. I a

What I claim is:

1. In an automatic draft regulator and in combination with a smoke pipe having a side inlet opening to the atmosphere, a damper to open and close said inlet, a supporting frame mounted in said inlet and disposed in a Vertical plane, said frame marginally embordering the damper, and a pivotal supporting means in said frame for said damper affording an axis of rotation therefor which is inclined at an acute angle to the face of the damper.

2. In an automatic draft regulator and in combinationwith a smoke pipe having a side inlet opening to the atmosphere, a damper to open and close said inlet, a supporting frame mounted in said inlet and disposed in a vertical plane, said frame marginally embordering the damper, and a pivotal supporting means in said frame for said damper affording an axis of rotation therefor which is inclined at an acute angle to the Vertical center line of the damper and at an acute angle to the face of the damper. a

3. In an automatic draft regulator and in com-- bination with a smoke pipe having a side inlet opening to the atmosphere, a damper to open and close said inlet, a supporting frame mounted in said inlet and disposed in a vertical plane, said frame marginally embordering the damper, bearings in saidframe located at unequal axial distances from one end face thereof, and means fixed to said damper and pivotally mounted in said bearings.

4. In an automatic draft regulator and in combination with a smoke pipe having a side inlet opening to the atmosphere, a damper to open and close said inleiaia supporting frame mounted in said inlet and disposed in a vertical plane, said frame marginally embordering the damper, bearings in said frame located at unequal distances from the vertical center line of said frame and also at unequal axial distances from one end face of said frame, and means fixed to said damper and pivotally mounted in said bearings. I

5. In an automatic draft regulator, an annular supporting member adapted to be mounted in a vertical plane, a damper mounted concentrically in said member and also in said plane when the damper is in closed position, upper and lower bearings in said member, and means on said damper for pivotal engagement with said bearings, said means affording an axis of rotation for the damper which crosses the circular face thereof as a chord, said lower bearing being spaced a greater distance from the face of the damper than the upper bearing.

6. In an automatic draft regulator, an annular supporting member adapted to be mounted in a vertical plane, a damper mounted concentrically in said member and also in said plane when the damper is in closed position, upper and lower bearings in said member, and means on said damper for pivotal engagement with said bearings, said means affording an axis of rotation for the damper which crosses the circular face thereof as a chord, said bearings being spaced from the vertical diameter of said member and the upper bearing being more remote from such diameter than the lower bearing.

7. In an automatic draft regulator, an annular supporting member adapted to be mounted in a vertical plane, a damper mounted concentrically in said member and also in said plane when the damper is in closed position, upper and lower bearings in said member, and means on said damper for pivotal engagement with said bearings, said means affording an axis of rotation for the damper which crosses the circular face thereof as a chord, said bearings being spaced from the vertical diameter of said member and the upper bearing being more remote from such diameter than the lower bearing, said lower bearing being spaced a greater distance from the face of the damper than the upper bearing.

8. In an automatic draft regulator, a damper, a supporting frame marginally embordering the damper, a pivotal supporting means in said frame for said damper affording an axis of rotation therefor which is inclined at an acute angle to the face of the damper, and means for varying the angular relation between said face and axis.

LEOLYN F. SPEAR. 

